It is necessary for the mobile communication system to support UE mobility. In order to support UE mobility, the UE persistently measures not only the quality of a serving cell that currently provides a service but also the quality of a neighbor cell of the serving cell. The UE transmits the measurement result to the network at an appropriate time, and the network transmits a handover (HO) command and the like to the UE on the basis of the measurement result value reported by the UE and provides optimum mobility to the UE.
In order to support UE mobility as well as to provide information that is helpful to enterprise network management, the UE may perform a measurement procedure having a specific purpose established in the network or may report the measurement result to the network. For example, the UE receives broadcast information of a specific cell decided by the network. The UE may report a cell identity (also called a global cell ID) of the specific cell, location identification information (e.g., a tracking area code) of the specific cell, and/or other cell information (e.g., indicating a member or non-member of a Closed Subscriber Group (CSG) cell to a serving cell.
If the moving UE confirms a poor quality of a specific region through measurement, and may report location information and cell-quality measurement results of poor-quality cells to the network. The network may optimize the network on the basis of the cell-quality measurement result of UEs assisting network management. In a mobile communication system having a frequency reuse factor of 1, mobility is mostly performed between different cells in the same band. Therefore, in order to guarantee UE mobility, the UE has to accurately measure not only a quality of each neighbor cell having the same intermediate frequency as that of the serving cell, but also each cell information. In this way, measurement of a cell that has the same intermediate frequency as that of the serving cell is referred to as intra-frequency measurement. The UE performs intra-frequency measurement, and reports the cell quality measurement result to the network at an appropriate time, such that the quality measurement result of the corresponding cell can be achieved.
A mobile communication enterprise may operate and manage a network using a plurality of frequency bands. In order to guarantee optimum UE mobility under the condition that a service of the communication system is provided through multiple frequency bands, the UE has to measure not only the quality of each neighbor cell having an intermediate frequency different from that of the serving cell but also each piece of cell information. Likewise, measurement of a cell having an intermediate frequency different from that of the serving cell is referred to as inter-frequency measurement. The UE performs inter-frequency measurement such that it has to report the cell quality measurement result to the network at an appropriate time.
If the UE supports measurement of a heterogeneous network, it may measure the heterogeneous cell according to BS or eNB setting. Heterogeneous network measurement is referred to as inter-RAT (inter—Radio Access Technology) measurement. For example, RAT may include UTRAN (UMTS Terrestrial Radio Access Network) and (GSM EDGE Radio Access Network (GERAN) that are based on the 3GPP standard specification. If necessary, the RAT may further include a CDMA 200 system based on the 3GPP2 standard specification.